They would gain access as pizza delivery boys; they would be armed with assault weapons, and they would seek to kill as many as they could before they were overpowered, or killed.

News agencies report that authorities have arrested Eljvir Duka, 23, Dritan Duka, 28, and Shain Duka, 26, all natives of the former Yugoslavia residing illegally in the United States.

Mohamad Ibrahim Shnewer, 22, a native of Jordan, and Serdar Tatar, 23, originally from Turkey, have also been arrested for complicity in the same plot; Agron Abdullahu, 24, who like the Duka brothers was born in Yugoslavia, has been charged with aiding and abetting the Duka brothers' illegal possession of weapons. These three men are legal residents.

The Federal Bureau of Investigation, which cracked the case and filed a criminal complaint on Tuesday, May 8, said Tatar's father owned Super Mario's restaurant, near Fort Dix, that made regular deliveries to the military base, and also to the nearby McGuire air force base.

According to the FBI complaint, Tatar acquired a map of the cantonment area of Fort Dix, ostensibly so pizza delivery boys could find their way around the base, and copied it for his fellow conspirators.

Agencies quote FBI special agent J P Weis, in charge of the agency's Philadelphia field office, as saying the case highlights a new form of terrorism, where 'they operate under the radar...they strike when they feel it is right, whenever that might be.'

For Tatar's father, who is reportedly cooperating with the investigating authorities, the arrest of his son and friends has come as a shock.

ABC News quotes him as saying he had talked to his son the day before the arrests, and there was no indication of anything unusual.

He had no inkling, Tatar's father says, that his son harboured such a deep hatred for the United States. 'There's something wrong here,' ABC quotes the father as saying. 'I came here from Turkey in 1992, and this is my country. I love this country.'

The FBI, however, indicates that it was no bolt from the blue -- the investigation has been ongoing for 17 months.

It was triggered when a photo shop clerk alerted authorities to a 'disturbing' video brought in by one of the suspects. The video depicted 10 young men, all in their 20s, shooting off assault weapons at a firing range, while calling for jihad.

The investigation relied on electronic eavesdropping, and an informant who infiltrated the group. The complaint says Tatar allegedly was aware of, or at least suspicious of, the informant, and had on one occasion contacted a sergeant in the Philadelphia police department to check the informant's credentials.

The FBI busted the terrorist cell once the members finalised the surveillance part of the plan, and decided on Fort Dix as the target.

Shnewer, regarded as the group's ringleader, reportedly said the aim was to kill at least 100 soldiers.

Photograph: William Thomas Cain/Getty Images